The present application relates generally to an improved data processing apparatus and method and more specifically to mechanisms for precision adaptive vehicle trajectory query plan optimization.
Vehicle trajectory query is a fundamental function in connected vehicle solutions, while tremendous data size is a very big challenge for both query accuracy and performance. Such an application may consider gigabytes of data per day and terabytes of data per month for 10,000 vehicles.
Indexing is a widely used technology approach in both relational databases and No-SQL (no Structured Query Language) databases to accelerate queries. A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure. Indexes are used to quickly locate data without having to search every row in a database table every time a database table is accessed. Indexes can be created using one or more columns of a database table, providing the basis for both rapid random lookups and efficient access of ordered records.
A bitmap index is a special kind of index that stores the bulk of its data as bit arrays (bitmaps) and answers most queries by performing bitwise logical operations on these bitmaps. The most commonly used indexes, such as B+trees, are most efficient if the values they index do not repeat or repeat a smaller number of times. In contrast, the bitmap index is designed for cases where the values of a variable repeat very frequently. For example, the gender field in a customer database usually contains at most three distinct values: male, female or other. For such variables, the bitmap index can have a significant performance advantage over the commonly used trees. A reverse key index (i.e., R+tree) reverses the key value before entering it in the index. E.g., the value 24538 becomes 83542 in the index. Reversing the key value is particularly useful for indexing data such as sequence numbers, where new key values monotonically increase.